The DKM 3 is a compact and stable instrument suitable for first and second order
triangulations that weighs 20 pounds, and that reads direct to 0.5 seconds and by estimation to
0.05 seconds. Kern introduced the form in 1956, noting that they planned to build about 50 units
a year. Like the double circle theodolites that Heinrich Wild designed for Kern in the late 1930s,
the DKM 3 uses glass circles and an optical micrometer. Here, however, the telescope has a
relatively large aperture (72 mm), long effective optical path (24 inches), but a short length
overall (6 inches) so that it can transit in either direction.
The United States National Imagery and Mapping Agency, a successor to the Defense
Mapping Agency, transferred this DKM 3 to the Smithsonian. It was probably made in 1969 for
the Geodetic Survey Squadron, a branch of the United States Air Force that became part of the
DMA when that organization was formed in 1972. A decal on the shipping case reads
"DEFENSE MAPPING AGENCY, GEODETIC SURVEY SQUADRON."
Ref: "Kern Theodolite Splits a Second," Engineering News Record (February 16, 1956).